The present invention relates generally to switch matrices, and more particularly, to a scalable switch matrix and demodulator bank configuration for a high capacity multi-beam satellite uplink receiver.
Generally, satellite uplink receivers are typically used to receive one or more uplink transmission beams carrying radio frequency signals. The receivers demodulate the signals for further processing, and transmit the data to downlink modulators for transmission on downlink beams. So far the satellites have been designed to process a relatively small number of uplink transmission beams. As a result, satellite uplink receivers generally have dedicated demodulators for each potential uplink transmission beam.
In order to increase the capacity and reuse the uplink spectrum frequently and efficiently, there has been growing interest in developing satellites capable of processing several hundred uplink beams. Each beam can potentially carry traffic up to the capacity of the full uplink spectrum. However, due to limitations on frequency re-use and satellite processing power, the total footprint capacity is generally much less than the maximum beam capacity times the number of transmission beams. Accordingly, in a satellite system designed to process, for example, 400 uplink beams each having 12 sub-bands, 4800 dedicated demodulators would be required. Because the maximum capacity is much less than the 4800 potential communication sub-bands, however, many demodulators would be underutilized and, even at maximum footprint traffic, many demodulators would be idle.
As a result of low utilization rates, a dedicated demodulator architecture has the drawbacks of relatively high power consumption and undesirable added weight to the satellite.
The traffic of a beam varies with the demand, time-of-day, and/or motion of the satellite (in the case of non-geosynchronous satellites). Thus, there exists a need for an uplink architecture with a pool of demodulators that can be assigned dynamically to the beams based on their needs. A scalable switch matrix provides reliable uplink signal processing, and reduces the amount of required hardware versus dedicated demodulator architectures, thereby eliminating additional power, volume, mass, and complexity.
The present invention has several advantages over existing architectures. The present invention is a scalable switch matrix and demodulator bank architecture for a satellite payload processor wherein the demodulators are connected to the output ports of the switches and assigned optimally to the beams as the load on the uplink beams varies. Thus, a smaller number of demodulators are required to process the uplink signals. This results in a readily scalable architecture having higher utilization of the demodulators, smaller switch sizes, and a higher efficiency and overall reliability.
These advantages are accomplished through the use of a high capacity switch matrix for processing data from many uplink transmission beams wherein each of the transmission beams is capable of carrying an active communication signal in any one of several sub-bands.
The switch matrix includes a first switch layer including one or more switches, each having several inputs and outputs. Each of the switch inputs are connected to receive one of the uplink transmission beams such that the total number of switch inputs is greater than or equal to the number of uplink input transmission beams. The switch matrix also includes a plurality of demodulators for retrieving data from the active communication sub-bands of the transmission beams. The total number of demodulators is limited to the maximum number of communication sub-bands which can be active at any one given time. This number is generally much less than the number of sub-bands per beam times the number of uplink transmission beams.
A second switch layer is connected between the first switch layer and the demodulators. The second switch layer includes groups of varying numbers of switches such that the output ports of the first switches are connected to a varying number of demodulators. Thus, when a first switch receives uplink transmission beams having many active communication sub-bands, it routes the data traffic to an output port having a corresponding number of demodulators.
In another aspect of the invention, a tandem switch is configured parallel to the first switch layer and is used to direct overflow traffic to underutilized switches in the first switch layer. This arrangement of the switch matrix allows any of the uplink transmission beams to be connected to a time-varying number of demodulators. Other advantages of the invention will become apparent when viewed in light of the following detailed description and appended claims, and upon reference to the accompanying drawings.